1. Field of the Invention
The present invention relates generally to diagnostic systems for exercising and evaluating characteristics and capacity of the human body during lifting. More particularly, the invention relates to an improved machine, system and method for determining characteristics of a patient's body during lifting exercises.
2. Description of Related Technology
In the field of exercise physiology, one type of resistance to muscular exertion is known as isometric resistance. Isometric resistance is designed to preclude movement at any level of exertion by the user. More specifically, it is the attempted motion of a stationary object where the length of the muscle fibers involved in the exercise does not change.
Isometric resistance has been utilized in the past to analyze the human body during lifting operations. Examples of currently available products that utilize isometric resistance are the ISTU manufactured by Ergometrics Inc. and the Arcon ST by Applies Rehabilitation Concepts. While these systems have been useful for some purposes, they suffer a number of disadvantages.
In particular, diagnostic systems which employ isometric resistance are unable to evaluate certain types of injuries, such as the injuries where a patient only experiences pain during actual movement of an affected body part. Moreover, since isometric systems are static, they are unable to accurately project a patient's actual dynamic lifting capacity. It is well known in the art that the strength of a particular body part varies depending upon the positioning of that body part. Testing systems that employ isometric resistance are typically limited to one exercise position. Therefore, these systems are insufficient to accurately determine a patient's dynamic lifting capacity. Furthermore, since isometric systems do not involve any muscular movement of the patient, these systems lack the capacity to accurately evaluate muscular endurance.
An alternate means for resistance muscular exertion, in contrast to isometric resistance, is dynamic resistance. Dynamic resistance is resistance permitting actual movement of an object by a person exerting force against it. Dynamic resistance involves the shortening and lengthening of the person's muscle fibers. Today it is generally understood that there are three basic types of dynamic resistance; isotonic, isokinetic and isodynamic.
Isotonic resistance involves the use of gravity or the simulation of gravity to resist muscular exertion. Some examples of exercise equipment utilizing isotonic resistance include free weights such as barbells, as well as Universal brand weight lifting machines. While the forces of gravity remain constant, the resistance to motions, such as lifting, varies during the movement because of the skeletal angle changes.
Muscle movement against isotonic resistance occurs in two categories. First, the contractile phase involves shortening the muscle fibers while the weight is moved against gravity, or in other words "lifting" the weight. Second, the eccentric phase refers to motion wherein the muscle fibers are lengthened while the weight is moved in the same direction as the force of gravity, or in other words "lowering" the weight.
Exercise machines that provide isotonic resistance by using resistance other than weights are well known in the art. For example, a hydraulic source used to supply isotonic resistance is disclosed in U.S. Pat. No. 4,865,315 to Paterson et al., entitled "Dedicated Microprocessor Controlled Exercise Resistance Machine." In addition to hydraulic sources, isotonic resistance has been provided by pneumatic sources, as illustrated in U.S. Pat. No. 4,257,593 to Keiser, entitled "Pneumatic Exercising Device".
Exercise apparatuses that provide isotonic resistance have been adequate for some purposes. For example, machines that provide isotonic resistance are able to duplicate the resistance encountered when lifting a physical object against gravity. Therefore, these systems can resemble "real life" situations.
Isokinetic resistance, as now understood, restricts motion to approximately constant velocity, irrespective of the amount of force applied by the patient. Exercise machines that provide isokinetic resistance are well known in the art, and have used a number of different means for resistance. For example, systems are known that provide adjustable isokinetic resistance with mechanical or electric braking devices. Additionally, hydraulic sources have been used in the provision of isokinetic resistance. An example of an exercise machine that provides isokinetic resistance is the Cybex Liftask brand system, which is sold by Lumex Industries. Another example of an apparatus that provides isokinetic resistance to exercise is the Biodex dynamometer sold by Biodex Corp. of Shirely, N.Y. The biodex dynamometer adapts to provide isokinetic resistance for use in quantifying flexion and extension movements of a patient's lower spine and other rotational movements about an isolated single axis such as knee flexion/extension.
Exercise machines that provide isokinetic resistance have been sufficient for some purposes. Specifically, users of exercise or quantitative machines that utilize isokinetic resistance have enjoyed a substantial degree of safety, since they are free to exert as much or as little force against the resistance as they wish without altering their rate of motion. Isodynamic resistance, or alternately, isoinertial resistance, exerts an approximately constant force during exercise, thereby allowing for changes in acceleration and velocity of motion in proportion to the force applied by the user. Isodynamic devices previously were also referred to as "isokinetic" and a distinctions between the two has only recently been recognized by the industry.
Exercise machines providing isodynamic resistance are known in the art. For example, U.S. Pat. No. 4,733,859 to Kock et al., entitled "Exercise Apparatus" utilizes isodynamic resistance in conjunction with neck or foot exercise. Isodynamic resistance has been useful in a number of applications, and is considered reasonably similar to "real world" lifting conditions because this resistance allows changes in movement velocity in proportion to changes in muscular force. Isodynamic systems have been used to obtain measurements such as the velocity of the weight lifted and the torque on an exercising joint, in order to evaluate a patient's level of impairment or to monitor a patient's recovery.
Exercise and quantitative machines for lifting movements utilizing isometric, isokinetic, or isotonic resistance modes have been used with some success, but the measurements they provide are not as versatile or comprehensive as might be desired in some contexts. In particular, these machines lack versatility if they only offer a single mode of resistance or limited options. Thus, the evaluations performed with these machines are not as useful as needed for some applications.
There are presently a number of machines that can furnish multiple modes of exercise resistance. Two examples of machines that facilitate neck exercise against dynamic or isometric resistance are U.S. Pat. No. 4,768,779 to Oehman, Jr. et al., entitled "Back Exercise Apparatus with a Neck Exercise Attachment" and U.S. Pat. No. 4,893,808 to McIntyre et al., entitled "Exercise Apparatus For the Neck" are examples. The Oehman, Jr. et al. and McIntyre machines also supply data in order to facilitate the computerized determination of parameters associated with the exercise, such as angular position, velocity, and torque. In addition, there are machines which apparently do provide multiple modes of resistance, such as LIDO Lift by Loredan, Kin-Com by Chattex, and Isonertial Lift Device by Baltimore Therapeutics, but none of those devices offer the potential for assessing weight distribution during lifting.
In addition, Cybex, a division of Lumex Industries, makes the Liftask device, which is a dynamic cable-actuated lifting platform that is based on isokinetic resistance. While the Lifttask device does allow the torque curve for the entire multi-joint lifting motion to be measured, the unit will not provide isoinertial resistance and therefore any potential information associated with velocity and acceleration measures against a constant force cannot be examined. It is known that velocity and acceleration measures are sensitive indicators of consistent effort, which is important is ascertaining malingering, one goal of the claimed invention.
Although the above-described systems have often been satisfactory for their intended purposes, they all share a number of disadvantages when considered for some uses. In particular, none of these machines accurately simulate occupational conditions where various objects are lifted in an unconstrained environment. Accordingly, a system is needed in order to provide data relating to the musculoskeletal activity of a patient during weight lifting exercises similar to the lifting of objects. Additionally, it would be beneficial to rehabilitation and evaluation to have a system that provides a comprehensive report of the velocity, magnitude, a real-time position of the weight lifted during such exercises.
Another limitation of present exercise and diagnostic systems is that they do not provide any information relating to an exercising patient's weight and force distributions during lifting-type exercise. In U.S. Pat. No. 4,738,269 to Nashner, entitled "Apparatus and Method for Sensory Integration and Muscular Coordination Analysis", an irregularly moving rectangular platform having a total of four pressure sensors positioned with two independently connected under each foot in conjunction with various sensory inputs is used to test a patient's ability to maintain his/her equilibrium. Systems such as that of Nashner, although adequate for their intended purposes, lack usefulness in qualifying a patient's weight distribution placed on his/her feed during lifting exercise. Such information would be valuable in determining musculoskeletal strategies for the patient to maintain proper balance, prevent injuries, and minimize the pain caused by existing physiological problems. Therefore, it would be beneficial to have a system, such as a weight lifting platform, capable of supplying detailed information about the patient's weight distribution during lifting exercises.
Furthermore, feedback concerning the musculoskeletal condition of a patient during lifting exercises would be valuable for conducting calculations such as joint torques and spinal compressions during movement. However, the ability of the present technology to provide such information is limited. Therefore, it would be of distinct value to have a system that provides a comprehensive musculoskeletal analysis of the user during lifting exercising, so that condition such joint stress, spinal compression, and the like can be evaluated.
It would also be advantageous to have an evaluation system that selectively provides isometric, isotonic, isokinetic, or isodynamic resistance, and additionally supplies sufficient data for analysis of muscular endurance, maximal dynamic lifting capacity, and weight distribution. Also, it would be beneficial to help evaluate injuries related to specific conditions and ranges of movement.